The $χ_{c1}(4274)$ multiplicity in heavy-ion collisions

Abstract: In a previous work we computed the thermally-averaged cross sections for the production and absorption of the $\chi_{c1}(4274)$ state in the hot hadron gas formed in heavy ion collisions. In the present work we estimate the final yield of this exotic state in these collisions. We use the coalescence model to fix the initial multiplicities. The state is is treated as a $P-$wave bound state of $D_s\bar D_{s0}$ and also as a compact tetraquark. The Bjorken picture is used to model the hydrodynamic expansion and cooling. Then, the kinetic equation is solved to evaluate the time evolution of the $\chi_{c1}(4274)$ yield during the hot hadron gas phase. Since the $\chi_{c1}(4274)$ decay width is large it might decay inside the hadron gas. Therefore we also include the $chi_{c1}(4274)$ decay and regeneration terms by means of an effective coupling, estimated from the available data. The combined effects of hadronic interactions and the $\chi_{c1}(4274)$ decay have a strong impact on the final yield. Also, predictions of the $\chi_{c1}(4274)$ multiplicity as a function of centrality and of the charged hadron multiplicity (measured at midrapidity) are presented. Finally, we calculate the yield of a proposed $P-$wave molecular state of $D_s \bar{D_{s0}}$, $Y<sup>{\prime}(4274)$, characterized by a smaller width and smaller coupling constant obtained from the Weinberg compositeness condition.